Composite substrate, epitaxial structure and device

Abstract

The utility model relates to a composite substrate, an epitaxial structure and a device, in particular to the field of power devices, and the composite substrate comprises a polycrystalline SiC layer, a first 4H-SiC layer, a 3C-SiC layer and a second 4H-SiC layer which are arranged in sequence. According to the composite substrate provided by the utility model, the quantum well is formed on the connection interface of the 3C-SiC layer and the 4H-SiC layer by adopting a specifically designed structure, and the fault is expanded to the connection interface, so that the fault is prevented from being expanded to a single crystal layer and even an epitaxial layer, the pressure resistance is improved, and meanwhile, the obtained composite substrate has relatively low surface free energy, so that the performance of the device is improved. The thin single crystal layer can be prevented from being etched through.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of power device, concretely relates to a composite substrate, epitaxial structure and device, especially relates to a composite substrate, epitaxial structure and device for MOSFET. BACKGROUND

[0002] Silicon carbide is a kind of wide band gap semiconductor material, and the device made of silicon carbide substrate has the advantages of high temperature resistance, high pressure resistance, high frequency, high power, radiation resistance and high efficiency, and has important application value in the field of radio frequency, new energy automobile and the like.

[0003] At present, in 750V MOSFET, the drift region thickness is only 6-8 μm, and the substrate will contribute up to 17% of the total resistance of the device. When the traditional single crystal SiC substrate is grown by seed sublimation, there is a basic trade-off between crystal quality (low defect density) and doping density (low resistivity). Since the substrate is the basis for subsequent epitaxial growth, the quality of the substrate cannot be affected, so its resistance is relatively high (usually 15-25 mOhm-cm). The limited doping density of the substrate also increases the small contact resistance (Rc) between the substrate and the drain. On the contrary, when producing polycrystalline silicon carbide substrates, the defect density is not important, so the doping density can be pushed to the limit, thereby minimizing its resistance.

[0004] Therefore, by processing a high-quality silicon carbide single crystal substrate, bonding the processed surface to a low-resistance polycrystalline silicon carbide wafer as a supporting substrate, not only can reduce the cost, but also can reduce the on-resistance and provide device performance.

[0005] However, the existing bonded substrate still has the defects of poor voltage resistance and easy etching through during epitaxial growth and etching. UTILITY MODEL CONTENTS

[0006] In view of the problems in the prior art, the purpose of the utility model is to provide a composite substrate, epitaxial structure and device to solve the defects of the existing bonded substrate, such as poor voltage resistance and easy etching through during epitaxial growth and etching.

[0007] To achieve this purpose, the utility model adopts the following technical solutions:

[0008] In the first aspect, the utility model provides a composite substrate, which comprises: a polycrystalline SiC layer, a first 4H-SiC layer, a 3C-SiC layer and a second 4H-SiC layer arranged in sequence.

[0009] The thickness of the polycrystalline SiC layer is greater than the thickness of the first 4H-SiC layer, the 3C-SiC layer and the second 4H-SiC layer, respectively.

[0010] The composite substrate provided by the utility model has a lower surface free energy, can prevent the thin single crystal layer from being engraved through, and has improved voltage resistance performance.

[0011] As the preferred technical scheme of the utility model, the thickness of the polycrystalline SiC layer is 330-370 mu m.

[0012] As the preferred technical scheme of the utility model, the thickness of the first 4H-SiC layer is 0.3-0.7 mu m.

[0013] As the preferred technical scheme of the utility model, the thickness of the 3C-SiC layer is 0.3-0.7 mu m.

[0014] As the preferred technical scheme of the utility model, the thickness of the second 4H-SiC layer is 0.3-0.7 mu m.

[0015] In the second aspect, the utility model provides an epitaxial structure, the epitaxial structure includes the composite substrate as the first aspect.

[0016] As the preferred technical scheme of the utility model, the epitaxial structure sequentially includes from bottom to top:

[0017] The composite substrate, the buffer layer, the first N type 4H-SiC layer, the second N type 4H-SiC layer, the first P type 3C-SiC layer and the second P type 3C-SiC layer.

[0018] The thickness of the first N type 4H-SiC layer is greater than the thickness of the second N type 4H-SiC layer.

[0019] As the preferred technical scheme of the utility model, the thickness of the buffer layer is 0.5-2 mu m.

[0020] The thickness of the N type 4H-SiC layer grown by the first N type 4H-SiC layer is 5-30 mu m.

[0021] The thickness of the N type 4H-SiC layer grown by the second N type 4H-SiC layer is 0.5-2 mu m.

[0022] As the preferred technical scheme of the utility model, the thickness of the P type 3C-SiC layer grown by the first P type 3C-SiC layer is 0.5-1 mu m.

[0023] The thickness of the P type 3C-SiC layer grown by the second P type 3C-SiC layer is 0.5-2 mu m.

[0024] In a third aspect, the utility model provides a kind of power device, and the power device includes the composite substrate as described in the first aspect.

[0025] Compared with prior art, the utility model has the following beneficial effects:

[0026] (1) the utility model provides the composite substrate, and it is for high doping concentration, N heavily doped polycrystalline SiC substrate, and the higher the doping concentration, the more dislocation, and dislocation will expand in substrate, and the power of dislocation expansion is quantum well mechanism, and the band gap difference of 3C-SiC / 4H-SiC is 0.9eV, then forms quantum well.The power of dislocation expansion is quantum well mechanism, form quantum well between interface, so that dislocation expands to interface, thereby avoiding dislocation to expand to single crystal layer, even epitaxial layer, thereby improving device withstand voltage performance, the breakdown voltage of the device obtained by using the specific substrate and epitaxial structure of the utility model is greater than or equal to 1657V, when using the specific substrate of the utility model, the breakdown voltage of the obtained device is greater than or equal to 1589V.

[0027] (2) the existing bonding substrate single crystal layer is relatively thin, and H2 etching condition is easy to etch through single crystal layer when conventional silicon carbide epitaxial growth, because the surface free energy is 123kJ / mol under pure H2 atmosphere;And the composite substrate provided by the utility model is under H2 / SiH4 atmosphere, the surface free energy is 207kJ / mol, and under H2 / C3H8 atmosphere, the surface free energy is 117.6kJ / mol;That is, the composite substrate of the utility model is etched under H2 / C3H8 atmosphere to reduce the surface free energy, which can prevent thin single crystal layer from being etched. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is the schematic diagram of the composite substrate provided by the utility model embodiment;

[0029] Figure 2 It is the schematic diagram of the epitaxial structure provided by the utility model embodiment.

[0030] In the drawing: 1, polycrystalline SiC layer, 2, first 4H-SiC layer, 3, 3C-SiC layer, 4, first 4H-SiC layer;

[0031] 100, composite substrate, 200, buffer layer, 300, first N type 4H-SiC layer, 400, second N type 4H-SiC layer, 500, first P type 3C-SiC layer, 600, second P type 3C-SiC layer.

[0032] The utility model is further described in detail as follows.But the following examples are only simple examples of the utility model, and do not represent or limit the protection scope of the utility model, and the protection scope of the utility model is subject to the claims. DETAILED DESCRIPTION

[0033] In order to better illustrate the utility model, facilitate understanding of the technical scheme of the utility model, the typical but non-limiting embodiments of the utility model are as follows:

[0034] The embodiment provides a composite substrate, as shown in the drawing, the composite substrate comprises: a polycrystalline SiC layer 1, a first 4H-SiC layer 2, a 3C-SiC layer 3 and a second 4H-SiC layer 4 arranged in sequence. Figure 1 The thickness of the polycrystalline SiC layer 1 is greater than the thickness of the first 4H-SiC layer 2, the 3C-SiC layer 3 and the second 4H-SiC layer 4 respectively.

[0035] The thickness of the polycrystalline SiC layer 1 is greater than the thickness of the first 4H-SiC layer 2, the 3C-SiC layer 3 and the second 4H-SiC layer 4 respectively.

[0036] The thickness of the polycrystalline SiC layer 1 is 330-370 μm, for example, can be 330 μm, 335 μm, 340 μm, 345 μm, 350 μm, 355 μm, 360 μm, 365 μm or 370 μm, but not limited to the listed values, other values not listed in the range also meet the requirements.

[0037] The thickness of the first 4H-SiC layer 2 is 0.3-0.7 μm, for example, can be 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm or 0.7 μm, but not limited to the listed values, other values not listed in the range also meet the requirements.

[0038] The thickness of the 3C-SiC layer 3 is 0.3-0.7 μm, for example, can be 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm or 0.7 μm, but not limited to the listed values, other values not listed in the range also meet the requirements.

[0039] The thickness of the second 4H-SiC layer 4 is 0.3-0.7 μm, for example, can be 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm or 0.7 μm, but not limited to the listed values, other values not listed in the range also meet the requirements.

[0040] Exemplarily, the utility model provides a preparation method of the aforementioned composite substrate, and the preparation method comprises:

[0041] The first 4H-SiC layer after the first ion implantation is bonded with the polycrystalline SiC layer, and then the first peeling and the first polishing are carried out to obtain a first bonding body.

[0042] The first bonding body and the 3C-SiC layer subjected to the second ion implantation are subjected to second bonding, and then subjected to second peeling and second polishing to obtain a second bonding body;

[0043] The second bonding body and the 4H-SiC layer subjected to the third ion implantation are subjected to third bonding, and then subjected to third peeling and polishing to obtain a composite substrate.

[0044] In the utility model, the polycrystalline SiC layer 1, the first 4H-SiC layer 2, the 3C-SiC layer 3 and the second 4H-SiC layer 4 used in the bonding process are optionally subjected to appearance detection, and the following conditions are ensured: no edge crack; cumulative area of hexagonal cavity < 0.05%; no polytype; cumulative area of visual inclusion < 0.05%; no scratch; no chipped edge with length or width ≥ 0.2mm; no surface contamination; surface roughness Ra < 0.3nm, Rmax < 3nm; face shape parameters-LTV ≤ 2.5μm, TTV ≤ 6um, Bo ≤ 25μm, Warp ≤ 35μm.

[0045] The 4H-SiC layer used in the first ion implantation includes N-doped concentration of 5×10 18 -1×10 19 atom / cm 3 , and <11-20> direction 4° 4H-SiC single crystal layer, for example, can be 5×10 18 atom / cm 3 , 5.5×10 18 atom / cm 3 , 6×10 18 atom / cm 3 , 6.5×10 18 atom / cm 3 , 7×10 18 atom / cm 3 , 7.5×10 18 atom / cm 3 , 8×10 18 atom / cm 3 , 8.5×10 18 atom / cm 3 , 9×10 18 atom / cm 3 , 9.5×10 18 atom / cm 3 or 1×10 19 atom / cm 3 , but is not limited to the listed values, and other unlisted values in the range also meet the requirements.

[0046] In the utility model, tom / cm 3atom / cm

[0047] atom / cm 15 atom / cm 2 atom / cm 15 atom / cm 2 atom / cm 15 atom / cm 2 atom / cm 15 atom / cm 2 atom / cm 15 atom / cm 2 atom / cm 15 atom / cm 2 atom / cm 15 atom / cm 2 atom / cm

[0048] atom / cm 2 atom / cm

[0049] atom / cm atom / cm

[0050] atom / cm atom / cm

[0051] atom / cm atom / cm

[0052] atom / cm atom / cm

[0053] atom / cm 2 atom / cm 2 atom / cm 2 atom / cm 2 atom / cm 22.4 J / m 2 2.6 J / m 2 2.8 J / m 2 or 3 J / m 2 etc., but are not limited to the listed numerical values, and other unlisted numerical values within the range are acceptable.

[0054] The first peeling temperature is 150-300℃, for example, it can be 150℃, 160℃, 180℃, 200℃, 220℃, 240℃, 260℃, 280℃ or 300℃, etc., but is not limited to the listed numerical values, and other unlisted numerical values within the range are acceptable.

[0055] The first peeling time is 30-45min, for example, it can be 30min, 32min, 34min, 36min, 38min, 40min, 42min, 44min or 45min, etc., but is not limited to the listed numerical values, and other unlisted numerical values within the range are acceptable.

[0056] The surface roughness Ra of the first bonding body after the first polishing is <0.2nm, for example, it can be 0.19nm, 0.18nm, 0.16nm, 0.14nm, 0.12nm, 0.1nm, 0.08nm, 0.06nm, 0.04nm, 0.02nm or 0.01nm, etc., but is not limited to the listed numerical values, and other unlisted numerical values within the range are acceptable.

[0057] The 3C-SiC layer used in the second ion implantation includes a <11-20> direction 4° 3C-SiC single crystal layer.

[0058] The second ion implantation has an implantation dose ≥10×10 15 atom / cm 2 , for example, it can be 10×10 15 atom / cm 2 , 12×10 15 atom / cm 2 , 14×10 15 atom / cm 2 , 16×10 15 atom / cm 2 , 18×10 15 atom / cm 2 or 20×10 15 atom / cm 2 , etc., but is not limited to the listed numerical values, and other unlisted numerical values within the range are acceptable.

[0059] The second ion implantation has an implantation energy of ≥80 keV, for example, 80 keV, 85 keV, 90 keV, 95 keV, 100 keV, 105 keV, 110 keV, 120 keV, or 150 keV, etc., but not limited to the listed values, and other unlisted values in this range are also acceptable.

[0060] The second ion implantation has an implantation angle of 5°-20°, for example, 5°, 6°, 8°, 10°, 12°, 14°, 16°, 18°, or 20°, etc., but not limited to the listed values, and other unlisted values in this range are also acceptable.

[0061] The second ion implantation has an implantation depth of 0.5-1 μm, for example, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, or 1 μm, etc., but not limited to the listed values, and other unlisted values in this range are also acceptable.

[0062] The second bonding includes Ar ion activation.

[0063] The second bonding has a bonding strength of >1.5 J / m 2 , for example, 1.6 J / m 2 , 1.8 J / m 2 , 2 J / m 2 , 2.2 J / m 2 , 2.4 J / m 2 , 2.6 J / m 2 , 2.8 J / m 2 , or 3 J / m 2 , etc., but not limited to the listed values, and other unlisted values in this range are also acceptable.

[0064] The second peeling has a temperature of 150-300 °C, for example, 150 °C, 160 °C, 180 °C, 200 °C, 220 °C, 240 °C, 260 °C, 280 °C, or 300 °C, etc., but not limited to the listed values, and other unlisted values in this range are also acceptable.

[0065] The second peeling has a time of 30-45 min, for example, 30 min, 32 min, 34 min, 36 min, 38 min, 40 min, 42 min, 44 min, or 45 min, etc., but not limited to the listed values, and other unlisted values in this range are also acceptable.

[0066] The surface roughness Ra of the second bonding body obtained after the second polishing is less than 0.2 nm, for example, 0.19 nm, 0.18 nm, 0.16 nm, 0.14 nm, 0.12 nm, 0.1 nm, 0.08 nm, 0.06 nm, 0.04 nm, 0.02 nm, or 0.01 nm, etc., but not limited to the listed values, and other values not listed in the range are also required.

[0067] The 4H-SiC layer used in the third ion implantation includes a 4° 4H-SiC single crystal layer in the off-11-20 direction.

[0068] The implantation dose of the third ion implantation is greater than or equal to 10×10 15 atom / cm 2 , for example, 10×10 15 atom / cm 2 , 12×10 15 atom / cm 2 , 14×10 15 atom / cm 2 , 16×10 15 atom / cm 2 , 18×10 15 atom / cm 2 , or 20×10 15 atom / cm 2 , etc., but not limited to the listed values, and other values not listed in the range are also required.

[0069] The implantation energy of the third ion implantation is greater than or equal to 80 keV, for example, 80 keV, 85 keV, 90 keV, 95 keV, 100 keV, 105 keV, 110 keV, 120 keV, or 150 keV, etc., but not limited to the listed values, and other values not listed in the range are also required.

[0070] The implantation angle of the third ion implantation is 5°-20°, for example, 5°, 6°, 8°, 10°, 12°, 14°, 16°, 18°, or 20°, etc., but not limited to the listed values, and other values not listed in the range are also required.

[0071] The implantation depth of the third ion implantation is 0.5-1 μm, for example, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, or 1 μm, etc., but not limited to the listed values, and other values not listed in the range are also required.

[0072] The third bonding includes Ar ion activation.

[0073] The third bonding has a bonding strength > 1.5 J / m 2 , for example, 1.6 J / m 2 , 1.8 J / m 2 , 2 J / m 2 , 2.2 J / m 2 , 2.4 J / m 2 , 2.6 J / m 2 , 2.8 J / m 2 , or 3 J / m 2 , but not limited to the listed values, and other unlisted values within the range are also acceptable.

[0074] The third peeling has a temperature of 150-300°C, for example, 150°C, 160°C, 180°C, 200°C, 220°C, 240°C, 260°C, 280°C, or 300°C, but not limited to the listed values, and other unlisted values within the range are also acceptable.

[0075] The third peeling has a time of 30-45 min, for example, 30 min, 32 min, 34 min, 36 min, 38 min, 40 min, 42 min, 44 min, or 45 min, but not limited to the listed values, and other unlisted values within the range are also acceptable.

[0076] The third polishing results in a composite substrate with a surface roughness Ra < 0.2 nm, for example, 0.19 nm, 0.18 nm, 0.16 nm, 0.14 nm, 0.12 nm, 0.1 nm, 0.08 nm, 0.06 nm, 0.04 nm, 0.02 nm, or 0.01 nm, but not limited to the listed values, and other unlisted values within the range are also acceptable.

[0077] In the utility model, each operation process can be optionally cleaned, the number of particles with a diameter < 20 μm on the surface of the cleaning object is < 10 per piece, so as to avoid the adverse effect of the previous operation process on the subsequent operation, for example, at least 1 RCA standard cleaning is performed.

[0078] In the utility model, the bonding process is performed by a bonder, for example, the surface of a single crystal is attacked by an Ar ion beam to open a dangling bond, the surface is activated, and then the bonding is realized, but the bonding strength defined in the utility model needs to be ensured.

[0079] Further, the utility model provides an epitaxial structure, which comprises the composite substrate.

[0080] The epitaxial structure, for example,Figure 2 As shown, from bottom to top, sequentially comprises:

[0081] The composite substrate 100, the buffer layer 200, the first N-type 4H-SiC layer 300, the second N-type 4H-SiC layer 400, the first P-type 3C-SiC layer 500 and the second P-type 3C-SiC layer 600.

[0082] The thickness of the buffer layer 200 is 0.5-2 μm, for example, can be 0.5 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm or 2 μm, etc., but not limited to the listed values, other values not listed in the range also meet the requirements.

[0083] The thickness of the first N-type 4H-SiC layer 300 is 5-30 μm, for example, can be 5 μm, 6 μm, 7 μm, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm or 30 μm, etc., but not limited to the listed values, other values not listed in the range also meet the requirements.

[0084] The thickness of the second N-type 4H-SiC layer 400 is 0.5-2 μm, for example, can be 0.5 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm or 2 μm, etc., but not limited to the listed values, other values not listed in the range also meet the requirements.

[0085] The thickness of the first P-type 3C-SiC layer 500 is 0.5-1 μm, for example, can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm or 1 μm, etc., but not limited to the listed values, other values not listed in the range also meet the requirements.

[0086] The thickness of the second P-type 3C-SiC layer 600 is 0.5-2 μm, for example, can be 0.5 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm or 2 μm, etc., but not limited to the listed values, other values not listed in the range also meet the requirements.

[0087] Exemplarily, the utility model provides preparation method of foregoing epitaxial structure, preparation method includes:

[0088] Etching, buffer layer growth, first N-type 4H-SiC layer growth, second N-type 4H-SiC layer growth, first P-type 3C-SiC layer growth and second P-type 3C-SiC layer growth are sequentially carried out to the composite substrate, and epitaxial structure is obtained.

[0089] In the utility model, when preparing the epitaxial structure, the starting surface of the composite substrate is the surface of the second 4H-SiC layer 4, that is, when growing the buffer layer, the buffer layer 200 is grown on the surface of the second 4H-SiC layer.

[0090] The flow rate of the carrier gas used in the etching is 100-500 slm, for example, it can be 100 slm, 150 slm, 200 slm, 250 slm, 300 slm, 350 slm, 400 slm, 450 slm or 500 slm, but is not limited to the listed values, and other values not listed in the range also meet the requirements.

[0091] The flow rate of the carbon source gas used in the etching is 10-20 sccm, for example, it can be 10 sccm, 12 sccm, 14 sccm, 16 sccm, 18 sccm or 20 sccm, but is not limited to the listed values, and other values not listed in the range also meet the requirements.

[0092] The temperature of the etching is 1520-1580 DEG C, for example, it can be 1520 DEG C, 1525 DEG C, 1530 DEG C, 1535 DEG C, 1540 DEG C, 1545 DEG C, 1550 DEG C, 1555 DEG C, 1560 DEG C, 1565 DEG C, 1570 DEG C, 1575 DEG C or 1580 DEG C, but is not limited to the listed values, and other values not listed in the range also meet the requirements.

[0093] The pressure of the etching is 50-100 mbar, for example, it can be 50 mbar, 55 mbar, 60 mbar, 65 mbar, 70 mbar, 75 mbar, 80 mbar, 85 mbar, 90 mbar, 95 mbar or 100 mbar, but is not limited to the listed values, and other values not listed in the range also meet the requirements.

[0094] The time of the etching is 1-2 min, for example, it can be 1 min, 1.5 min or 2 min, but is not limited to the listed values, and other values not listed in the range also meet the requirements.

[0095] The flow rate of the carrier gas used in the buffer layer growth is 100-500 slm, for example, it can be 100 slm, 150 slm, 200 slm, 250 slm, 300 slm, 350 slm, 400 slm, 450 slm or 500 slm, but is not limited to the listed values, and other values not listed in the range also meet the requirements.

[0096] The flow rate of the silicon source gas used in the growth of the buffer layer is 50-100 sccm, for example, it can be 50 sccm, 60 sccm, 70 sccm, 80 sccm, 90 sccm or 100 sccm, etc., but is not limited to the listed values, and other values not listed in this range are also acceptable.

[0097] The flow rate of the carbon source gas used in the growth of the buffer layer is 30-80 sccm, for example, it can be 30 sccm, 40 sccm, 50 sccm, 60 sccm, 70 sccm or 80 sccm, etc., but is not limited to the listed values, and other values not listed in this range are also acceptable.

[0098] The flow rate of the N-type dopant used in the growth of the buffer layer is 20-30 sccm, for example, it can be 20 sccm, 22 sccm, 24 sccm, 26 sccm, 28 sccm or 30 sccm, etc., but is not limited to the listed values, and other values not listed in this range are also acceptable.

[0099] The growth temperature of the buffer layer growth is 1520-1580℃, for example, it can be 1520℃, 1525℃, 1530℃, 1535℃, 1540℃, 1545℃, 1550℃, 1555℃, 1560℃, 1565℃, 1570℃, 1575℃ or 1580℃, etc., but is not limited to the listed values, and other values not listed in this range are also acceptable.

[0100] The growth pressure of the buffer layer growth is 50-100 mbar, for example, it can be 50 mbar, 55 mbar, 60 mbar, 65 mbar, 70 mbar, 75 mbar, 80 mbar, 85 mbar, 90 mbar, 95 mbar or 100 mbar, etc., but is not limited to the listed values, and other values not listed in this range are also acceptable.

[0101] The thickness of the buffer layer obtained by the growth of the buffer layer is 0.5-2 μm, for example, it can be 0.5 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm or 2 μm, etc., but is not limited to the listed values, and other values not listed in this range are also acceptable.

[0102] The doping concentration of the buffer layer obtained by the growth of the buffer layer is 1×10 17 -2×10 18 atom / cm 3 , for example, it can be 1×10 17 atom / cm 3 , 2×1017 atoms / cm 3 , 4 x 10 17 atoms / cm 3 , 6 x 10 17 atoms / cm 3 , 8 x 10 17 atoms / cm 3 , 10 x 10 17 atoms / cm 3 , 12 x 10 17 atoms / cm 3 , 14 x 10 17 atoms / cm 3 , 16 x 10 17 atoms / cm 3 , 18 x 10 17 atoms / cm 3 or 2 x 10 18 atoms / cm 3 and so on, but are not limited to the listed values, other unlisted values within the range are also acceptable.

[0103] The flow rate of the carrier gas used in the growth of the first N-type 4H-SiC layer is 100-500 slm, for example, it can be 100 slm, 150 slm, 200 slm, 250 slm, 300 slm, 350 slm, 400 slm, 450 slm or 500 slm, and so on, but is not limited to the listed values, other unlisted values within the range are also acceptable.

[0104] The flow rate of the silicon source gas used in the growth of the first N-type 4H-SiC layer is 300-600 sccm, for example, it can be 300 sccm, 350 sccm, 400 sccm, 450 sccm, 500 sccm, 550 sccm or 600 sccm, and so on, but is not limited to the listed values, other unlisted values within the range are also acceptable.

[0105] The flow rate of the carbon source gas used in the growth of the first N-type 4H-SiC layer is 400-600 sccm, for example, it can be 400 sccm, 420 sccm, 440 sccm, 460 sccm, 580 sccm, 500 sccm, 520 sccm, 540 sccm, 560 sccm, 580 sccm or 600 sccm, and so on, but is not limited to the listed values, other unlisted values within the range are also acceptable.

[0106] The flow rate of the N-type dopant used in the growth of the first N-type 4H-SiC layer is 5-10 seem, for example, it can be 5 seem, 6 seem, 7 seem, 8 seem, 9 seem or 10 seem, etc., but is not limited to the listed values, and other values not listed in the range are also acceptable.

[0107] The growth temperature of the first N-type 4H-SiC layer is 1520-1580 °C, for example, it can be 1520 °C, 1525 °C, 1530 °C, 1535 °C, 1540 °C, 1545 °C, 1550 °C, 1555 °C, 1560 °C, 1565 °C, 1570 °C, 1575 °C or 1580 °C, etc., but is not limited to the listed values, and other values not listed in the range are also acceptable.

[0108] The growth pressure of the first N-type 4H-SiC layer is 50-100 mbar, for example, it can be 50 mbar, 55 mbar, 60 mbar, 65 mbar, 70 mbar, 75 mbar, 80 mbar, 85 mbar, 90 mbar, 95 mbar or 100 mbar, etc., but is not limited to the listed values, and other values not listed in the range are also acceptable.

[0109] The doping concentration of the N-type 4H-SiC layer obtained by growing the first N-type 4H-SiC layer is 0.5×10 16 -2×10 16 atom / cm 3 , for example, it can be 0.5×10 16 atom / cm 3 , 0.6×10 16 atom / cm 3 , 0.8×10 16 atom / cm 3 , 1×10 16 atom / cm 3 , 1.2×10 16 atom / cm 3 , 1.4×10 16 atom / cm 3 , 1.8×10 16 atom / cm 3 or 2×10 16 atom / cm 3 , etc., but is not limited to the listed values, and other values not listed in the range are also acceptable.

[0110] The flow rate of the carrier gas used in the growth of the second N-type 4H-SiC layer is 100-500 slm, for example, it can be 100 slm, 150 slm, 200 slm, 250 slm, 300 slm, 350 slm, 400 slm, 450 slm or 500 slm, etc., but not limited to the listed values, other values not listed in this range are also acceptable.

[0111] The flow rate of the silicon source gas used in the growth of the second N-type 4H-SiC layer is 300-600 sccm, for example, it can be 300 sccm, 350 sccm, 400 sccm, 450 sccm, 500 sccm, 550 sccm or 600 sccm, etc., but not limited to the listed values, other values not listed in this range are also acceptable.

[0112] The flow rate of the carbon source gas used in the growth of the second N-type 4H-SiC layer is 400-600 sccm, for example, it can be 400 sccm, 420 sccm, 440 sccm, 460 sccm, 580 sccm, 500 sccm, 520 sccm, 540 sccm, 560 sccm, 580 sccm or 600 sccm, etc., but not limited to the listed values, other values not listed in this range are also acceptable.

[0113] The flow rate of the N-type dopant used in the growth of the second N-type 4H-SiC layer is 5-10 sccm, for example, it can be 5 sccm, 6 sccm, 7 sccm, 8 sccm, 9 sccm or 10 sccm, etc., but not limited to the listed values, other values not listed in this range are also acceptable.

[0114] The growth temperature of the second N-type 4H-SiC layer is 1520-1580°C, for example, it can be 1520°C, 1525°C, 1530°C, 1535°C, 1540°C, 1545°C, 1550°C, 1555°C, 1560°C, 1565°C, 1570°C, 1575°C or 1580°C, etc., but not limited to the listed values, other values not listed in this range are also acceptable.

[0115] The growth pressure of the second N-type 4H-SiC layer is 50-100 mbar, for example, it can be 50 mbar, 55 mbar, 60 mbar, 65 mbar, 70 mbar, 75 mbar, 80 mbar, 85 mbar, 90 mbar, 95 mbar or 100 mbar, etc., but not limited to the listed values, other values not listed in this range are also acceptable.

[0116] The doping concentration of the N-type 4H-SiC layer obtained by growing the second N-type 4H-SiC layer is 2×10⁻⁶. 16 -4×10 16 atom / cm 3 For example, it could be 2×10 16 atom / cm 3 2.5×10 16 atom / cm 3 3×10 16 atom / cm 3 3.5×10 16 atom / cm 3 Or 4×10 16 atom / cm 3 The values ​​may include, but are not limited to, the listed values; other unlisted values ​​within this range also meet the requirements.

[0117] The flow rate of the carrier gas used in the growth of the first P-type 3C-SiC layer is 100-500 slm, for example, it can be 100 slm, 150 slm, 200 slm, 250 slm, 300 slm, 350 slm, 400 slm, 450 slm or 500 slm, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0118] The flow rate of the silicon source gas used in the growth of the first P-type 3C-SiC layer is 400-800 scmm, for example, it can be 400 sccm, 450 sccm, 500 sccm, 550 sccm, 600 sccm, 650 sccm, 700 sccm, 750 sccm or 800 sccm, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0119] The flow rate of the carbon source gas used in the growth of the first P-type 3C-SiC layer is 400-800 sccm, for example, it can be 400 sccm, 450 sccm, 500 sccm, 550 sccm, 600 sccm, 650 sccm, 700 sccm, 750 sccm or 800 sccm, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0120] The flux of the P-type dopant used in the growth of the first P-type 3C-SiC layer is 5-10 sccm, for example, it can be 5 sccm, 6 sccm, 7 sccm, 8 sccm, 9 sccm or 10 sccm, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0121] The growth temperature for growing the first P-type 3C-SiC layer can be 1350-1400 °C, for example, it can be 1350 °C, 1360 °C, 1370 °C, 1380 °C, 1390 °C, or 1400 °C, but is not limited to the listed values, and other values not listed in this range are also acceptable.

[0122] The growth pressure for growing the first P-type 3C-SiC layer can be 50-100 mbar, for example, it can be 50 mbar, 55 mbar, 60 mbar, 65 mbar, 70 mbar, 75 mbar, 80 mbar, 85 mbar, 90 mbar, 95 mbar, or 100 mbar, but is not limited to the listed values, and other values not listed in this range are also acceptable.

[0123] The growth rate for growing the first P-type 3C-SiC layer can be 1-2 μm / h, for example, it can be 1 μm / h, 1.2 μm / h, 1.4 μm / h, 1.6 μm / h, 1.8 μm / h, or 2 μm / h, but is not limited to the listed values, and other values not listed in this range are also acceptable.

[0124] The doping concentration of the P-type 3C-SiC layer obtained by growing the first P-type 3C-SiC layer can be 1 x 1010-2 x 1011atom / cm3, for example, it can be 1 x 1010atom / cm3, 1.2 x 1010atom / cm3, 1.4 x 1010atom / cm3, 1.6 x 1010atom / cm3, 1.8 x 1010atom / cm3, or 2 x 1010atom / cm3, but is not limited to the listed values, and other values not listed in this range are also acceptable. 16 -2 x 1011atom / cm3 16 atom / cm3 3 , for example, it can be 1 x 1010 16 atom / cm3 3 , 1.2 x 1010 16 atom / cm3 3 , 1.4 x 1010 16 atom / cm3 3 , 1.6 x 1010 16 atom / cm3 3 , 1.8 x 1010 16 atom / cm3 3 , or 2 x 1010 16 atom / cm3 3 , but is not limited to the listed values, and other values not listed in this range are also acceptable.

[0125] The flow rate of the carrier gas used in growing the second P-type 3C-SiC layer can be 100-500 slm, for example, it can be 100 slm, 150 slm, 200 slm, 250 slm, 300 slm, 350 slm, 400 slm, 450 slm, or 500 slm, but is not limited to the listed values, and other values not listed in this range are also acceptable.

[0126] The flow rate of the silicon source gas used in the growth of the second P-type 3C-SiC layer is 400-800 sccm, for example, it can be 400 sccm, 450 sccm, 500 sccm, 550 sccm, 600 sccm, 650 sccm, 700 sccm, 750 sccm, or 800 sccm, etc., but is not limited to the listed values, and other values not listed in this range are also acceptable.

[0127] The flow rate of the carbon source gas used in the growth of the second P-type 3C-SiC layer is 400-800 sccm, for example, it can be 400 sccm, 450 sccm, 500 sccm, 550 sccm, 600 sccm, 650 sccm, 700 sccm, 750 sccm, or 800 sccm, etc., but is not limited to the listed values, and other values not listed in this range are also acceptable.

[0128] The flow rate of the P-type dopant used in the growth of the second P-type 3C-SiC layer is 50-80 sccm, for example, it can be 50 sccm, 55 sccm, 60 sccm, 65 sccm, 70 sccm, 75 sccm, or 80 sccm, etc., but is not limited to the listed values, and other values not listed in this range are also acceptable.

[0129] The growth temperature of the second P-type 3C-SiC layer is 1350-1400°C, for example, it can be 1350°C, 1360°C, 1370°C, 1380°C, 1390°C, or 1400°C, etc., but is not limited to the listed values, and other values not listed in this range are also acceptable.

[0130] The growth pressure of the second P-type 3C-SiC layer is 50-100 mbar, for example, it can be 50 mbar, 55 mbar, 60 mbar, 65 mbar, 70 mbar, 75 mbar, 80 mbar, 85 mbar, 90 mbar, 95 mbar, or 100 mbar, etc., but is not limited to the listed values, and other values not listed in this range are also acceptable.

[0131] The growth rate of the second P-type 3C-SiC layer is 1-2 μm / h, for example, it can be 1 μm / h, 1.2 μm / h, 1.4 μm / h, 1.6 μm / h, 1.8 μm / h, or 2 μm / h, etc., but is not limited to the listed values, and other values not listed in this range are also acceptable.

[0132] The doping concentration of the P-type 3C-SiC layer obtained by growing the second P-type 3C-SiC layer is 1×10 17 -5×1017 atom / cm 3 For example, it can be 1 x 10 16 atom / cm 3 , 2 x 10 16 atom / cm 3 , 3 x 10 16 atom / cm 3 , 4 x 10 16 atom / cm 3 or 5 x 10 16 atom / cm 3 and the like, but is not limited to the listed values, other unlisted values within the range are also acceptable.

[0133] In the utility model, the carrier gas used in the epitaxial structure preparation includes hydrogen and other carrier gases commonly used in the field.

[0134] In the utility model, the silicon source gas used in the epitaxial structure preparation includes SiCl4, SiHCl3, SiH2C12 or SiH3Cl and other commonly used silicon source gases.

[0135] In the utility model, the carbon source gas used in the epitaxial structure preparation includes C2H2, C2H4, C3H8 and other commonly used carbon source gases.

[0136] In the utility model, the N-type dopant used in the epitaxial structure preparation includes N2 and / or NH3 and other commonly used N-type dopants.

[0137] In the utility model, the P-type dopant used in the epitaxial structure preparation includes TMAl and other commonly used P-type dopants.

[0138] Further, in order to illustrate the effect of the composite substrate provided by the utility model, the following actual examples are used for exemplary illustration, and the details are as follows:

[0139] Embodiment 1

[0140] The composite substrate provided in the embodiment includes: a polycrystalline SiC layer 1, a first 4H-SiC layer 2, a 3C-SiC layer 3 and a second 4H-SiC layer 4 which are sequentially bonded.

[0141] The thickness of the polycrystalline SiC layer 1 is 350 μm; the thickness of the first 4H-SiC layer 2 is 0.4 μm; the thickness of the 3C-SiC layer 3 is 0.6 μm; and the thickness of the second 4H-SiC layer 4 is 0.5 μm.

[0142] The preparation process is as follows:

[0143] bonding a first ion-implanted 4H-SiC layer and a poly-SiC layer to obtain a first bonding body, and then performing a first peeling and a first polishing;

[0144] bonding a first bonding body and a second ion-implanted 3C-SiC layer to obtain a second bonding body, and then performing a second peeling and a second polishing;

[0145] bonding a third ion-implanted 4H-SiC layer and the second bonding body to obtain a composite substrate, and then performing a third peeling and a polishing;

[0146] The 4H-SiC layer used in the first ion implantation has an N-doped concentration of 6×10 18 atom / cm 3 , and is a <11-20> direction 4° 4H-SiC single crystal layer; the first ion implantation has an implantation dose of 10×10 15 atom / cm 2 , an implantation energy of 80 keV, an implantation angle of 15°, and an implantation depth of 0.8 μm; the first bonding is performed by Ar ion activation, and has a bonding strength of 1.8 J / m 2 ; the first peeling is performed at a temperature of 200 °C for 40 min; and the first bonding body obtained after the first polishing has a surface roughness Ra of 0.15 nm;

[0147] The 3C-SiC layer used in the second ion implantation is a <11-20> direction 4° 3C-SiC single crystal layer; the second ion implantation has an implantation dose of 12×10 15 atom / cm 2 , an implantation energy of 85 keV, an implantation angle of 15°, and an implantation depth of 0.7 μm; the second bonding is performed by Ar ion activation, and has a bonding strength of 1.6 J / m 2 ; the second peeling is performed at a temperature of 200 °C for 40 min; and the second bonding body obtained after the second polishing has a surface roughness Ra of 0.18 nm;

[0148] The 4H-SiC layer used in the third ion implantation is a <11-20> direction 4° 4H-SiC single crystal layer; the third ion implantation has an implantation dose of 20×10 15 atom / cm 2 , an implantation energy of 90 keV, an implantation angle of 15°, and an implantation depth of 0.6 μm; the third bonding is performed by Ar ion activation, and has a bonding strength of 1.8 J / m 2 ; the third peeling is performed at a temperature of 250 °C for 35 min; and the composite substrate obtained after the third polishing has a surface roughness Ra of 0.14 nm.

[0149] The embodiment provides an epitaxial structure, which comprises, from bottom to top, successively:

[0150] The composite substrate 100, the buffer layer 200, the first N-type 4H-SiC layer 300, the second N-type 4H-SiC layer 400, the first P-type 3C-SiC layer 500 and the second P-type 3C-SiC layer 600.

[0151] The preparation process is as follows:

[0152] The composite substrate is subjected to etching, buffer layer growth, first 4H-SiC layer growth, second 4H-SiC layer growth, first P-type 3C-SiC layer growth and second P-type 3C-SiC layer growth successively to obtain the epitaxial structure;

[0153] In the etching, the flow rate of the carrier gas is 300 slm, the flow rate of the carbon source gas is 15 sccm, the temperature is 1540 ℃, the pressure is 60 mbar and the time is 1.5 min;

[0154] In the buffer layer growth, the flow rate of the carrier gas is 300 slm, the flow rate of the silicon source gas is 60 sccm, the flow rate of the carbon source gas is 40 sccm, the flow rate of the N-type dopant is 25 sccm, the growth temperature is 1540 ℃, the growth pressure is 60 mbar, the thickness of the obtained buffer layer is 1 μm and the doping concentration of the obtained buffer layer is 1.5×10 18 atom / cm 3 ;

[0155] In the first N-type 4H-SiC layer growth, the flow rate of the carrier gas is 300 slm, the flow rate of the silicon source gas is 400 sccm, the flow rate of the carbon source gas is 500 sccm, the flow rate of the N-type dopant is 6 sccm, the growth temperature is 1540 ℃, the growth pressure is 60 mbar, the thickness of the obtained N-type 4H-SiC layer is 10 μm and the doping concentration of the obtained N-type 4H-SiC layer is 1×10 16 atom / cm 3 ;

[0156] In the second N-type 4H-SiC layer growth, the flow rate of the carrier gas is 300 slm, the flow rate of the silicon source gas is 400 sccm, the flow rate of the carbon source gas is 500 sccm, the flow rate of the N-type dopant is 6 sccm, the growth temperature is 1540 ℃, the growth pressure is 60 mbar, the thickness of the obtained N-type 4H-SiC layer is 1.5 μm and the doping concentration of the obtained N-type 4H-SiC layer is 3.5×10 16 atom / cm 3 ;

[0157] The flow rate of the carrier gas used in the growth of the first P-type 3C-SiC layer is 300 slm, the flow rate of the silicon source gas used is 600 sccm, the flow rate of the carbon source gas used is 600 sccm, the flow rate of the P-type dopant used is 6 sccm, the growth temperature is 1380°C, the growth pressure is 80 mbar, the growth rate is 1.5 μm / h, the thickness of the obtained P-type 3C-SiC layer is 0.8 μm, and the doping concentration of the obtained P-type 3C-SiC layer is 1.6 x 1019 atom / cm2. 16 ; 3 ;

[0158] The flow rate of the carrier gas used in the growth of the second P-type 3C-SiC layer is 300 slm, the flow rate of the silicon source gas used is 600 sccm, the flow rate of the carbon source gas used is 600 sccm, the flow rate of the P-type dopant used is 60 sccm, the growth temperature is 1380°C, the growth pressure is 80 mbar, the growth rate is 1.4 μm / h, the thickness of the obtained P-type 3C-SiC layer is 1.5 μm, and the doping concentration of the obtained P-type 3C-SiC layer is 4 x 1019 atom / cm2. 17 ; 3 ;

[0159] In this embodiment, the carrier gas used is hydrogen, the silicon source gas used is SiCl4, the carbon source gas used is C2H2, the N-type dopant used is N2, and the P-type dopant used is TMAl.

[0160] Example 2

[0161] The composite substrate provided in this embodiment comprises, in order: a polycrystalline SiC layer 1, a first 4H-SiC layer 2, a 3C-SiC layer 3, and a second 4H-SiC layer 4.

[0162] The thickness of the polycrystalline SiC layer 1 is 360 μm; the thickness of the first 4H-SiC layer 2 is 0.5 μm; the thickness of the 3C-SiC layer 3 is 0.5 μm; and the thickness of the second 4H-SiC layer 4 is 0.6 μm.

[0163] The preparation process is as follows:

[0164] The first bonding of the first ion-implanted 4H-SiC layer and the polycrystalline SiC layer is followed by first peeling and first polishing to obtain a first bonding body;

[0165] The second bonding of the first bonding body and the second ion-implanted 3C-SiC layer is followed by second peeling and second polishing to obtain a second bonding body;

[0166] The third bonding of the second bonding body and the third ion-implanted 4H-SiC layer is followed by third peeling and polishing to obtain a composite substrate;

[0167] The 4H-SiC layer used in the first ion implantation includes an N doping concentration of 8×10 18 atom / cm 3 , a <11-20> direction 4° 4H-SiC single crystal layer; the injection dose of the first ion implantation is 12×10 15 atom / cm 2 , the injection energy is 85 keV, the injection angle is 10°, and the injection depth is 0.7 μm; the bonding mode of the first bonding is Ar ion activation, and the bonding strength is 2 J / m 2 ; the temperature of the first peeling is 250 °C, and the time is 35 min; the surface roughness Ra of the first bonding body obtained after the first polishing is 0.13 nm;

[0168] The 3C-SiC layer used in the second ion implantation is a <11-20> direction 4° 3C-SiC single crystal layer; the injection dose of the second ion implantation is 14×10 15 atom / cm 2 , the injection energy is 80 keV, the injection angle is 10°, and the injection depth is 0.8 μm; the bonding mode of the second bonding is Ar ion activation, and the bonding strength is 1.8 J / m 2 ; the temperature of the second peeling is 250 °C, and the time is 35 min; the surface roughness Ra of the second bonding body obtained after the second polishing is 0.19 nm;

[0169] The 4H-SiC layer used in the third ion implantation is a <11-20> direction 4° 4H-SiC single crystal layer; the injection dose of the third ion implantation is 25×10 15 atom / cm 2 , the injection energy is 80 keV, the injection angle is 10°, and the injection depth is 0.7 μm; the bonding mode of the third bonding is Ar ion activation, and the bonding strength is 2.5 J / m 2 ; the temperature of the third peeling is 200 °C, and the time is 40 min; the surface roughness Ra of the composite substrate obtained after the third polishing is 0.12 nm.

[0170] The present embodiment provides an epitaxial structure, which comprises, from bottom to top, in sequence:

[0171] A composite substrate 100, a buffer layer 200, a first N-type 4H-SiC layer 300, a second N-type 4H-SiC layer 400, a first P-type 3C-SiC layer 500, and a second P-type 3C-SiC layer 600.

[0172] The preparation process is as follows:

[0173] etching, buffer layer growth, first 4H-SiC layer growth, second 4H-SiC layer growth, first P-type 3C-SiC layer growth and second P-type 3C-SiC layer growth to obtain an epitaxial structure;

[0174] The flow rate of the carrier gas used in the etching is 200 slm, the flow rate of the carbon source gas is 18 sccm, the temperature is 1560℃, the pressure is 80 mbar, and the time is 1.5 min;

[0175] The flow rate of the carrier gas used in the buffer layer growth is 200 slm, the flow rate of the silicon source gas used is 80 scmm, the flow rate of the carbon source gas used is 60 sccm, the flow rate of the N-type dopant used is 25 sccm, the growth temperature is 1560℃, the growth pressure is 80 mbar, the thickness of the obtained buffer layer is 1.5 μm, and the doping concentration of the obtained buffer layer is 1.8×10 18 atom / cm 3 ;

[0176] The flow rate of the carrier gas used in the first N-type 4H-SiC layer growth is 200 slm, the flow rate of the silicon source gas used is 500 scmm, the flow rate of the carbon source gas used is 550 sccm, the flow rate of the N-type dopant used is 8 sccm, the growth temperature is 1560℃, the growth pressure is 80 mbar, the thickness of the obtained N-type 4H-SiC layer is 20 μm, and the doping concentration of the obtained N-type 4H-SiC layer is 1.5×10 16 atom / cm 3 ;

[0177] The flow rate of the carrier gas used in the second N-type 4H-SiC layer growth is 200 slm, the flow rate of the silicon source gas used is 500 scmm, the flow rate of the carbon source gas used is 550 sccm, the flow rate of the N-type dopant used is 8 sccm, the growth temperature is 1560℃, the growth pressure is 80 mbar, the thickness of the obtained N-type 4H-SiC layer is 1 μm, and the doping concentration of the obtained N-type 4H-SiC layer is 3×10 16 atom / cm 3 ;

[0178] The flow rate of the carrier gas used in the first P-type 3C-SiC layer growth is 200 slm, the flow rate of the silicon source gas used is 500 scmm, the flow rate of the carbon source gas used is 500 sccm, the flow rate of the P-type dopant used is 8 sccm, the growth temperature is 1360℃, the growth pressure is 60 mbar, the growth speed is 1.5 μm / h, the thickness of the obtained P-type 3C-SiC layer is 0.6 μm, and the doping concentration of the obtained P-type 3C-SiC layer is 1.4×10 16 atom / cm 3 ;

[0179] The flow rate of the carrier gas used in the growth of the second P-type 3C-SiC layer was 200 slm, the flow rate of the silicon source gas was 500 scmm, the flow rate of the carbon source gas was 500 sccm, the flow rate of the P-type dopant was 70 sccm, the growth temperature was 1360℃, the growth pressure was 60 mbar, the growth rate was 1.6 μm / h, the thickness of the obtained P-type 3C-SiC layer was 1 μm, and the doping concentration of the obtained P-type 3C-SiC layer was 2 × 10⁻⁶. 17 atom / cm 3 ;

[0180] In this embodiment, the carrier gas used is hydrogen, the silicon source gas used is SiH3Cl, the carbon source gas used is C3H8, the N-type dopant used is NH3, and the P-type dopant used is TMAl.

[0181] Example 3

[0182] This embodiment provides a composite substrate, which includes: a polycrystalline SiC layer 1, a first 4H-SiC layer 2, a 3C-SiC layer 3, and a second 4H-SiC layer 4 bonded sequentially;

[0183] The polycrystalline SiC layer 1 has a thickness of 330 μm; the first 4H-SiC layer 2 has a thickness of 0.3 μm; the 3C-SiC layer 3 has a thickness of 0.7 μm; and the second 4H-SiC layer 4 has a thickness of 0.3 μm.

[0184] The preparation process is as follows:

[0185] The 4H-SiC layer implanted with the first ion is bonded to the polycrystalline SiC layer, and then subjected to the first peeling and the first polishing to obtain the first bonded body;

[0186] The first bonded body and the 3C-SiC layer implanted by the second ion are bonded together, followed by a second peeling and a second polishing to obtain the second bonded body;

[0187] The second bond and the 4H-SiC layer implanted by the third ion are bonded together in the third way, and then the composite substrate is obtained by third peeling and polishing.

[0188] The 4H-SiC layer used in the first ion implantation has an N-doping concentration of 5 × 10⁻⁶. 18 atom / cm 3 A 4° 4H-SiC single crystal layer with a bias of <11-20> direction; the implantation dose of the first ion implantation is 10 × 10⁻⁶. 15 atom / cm 2The injection energy was 80 keV, the injection angle was 5°, and the injection depth was 0.5 μm; the first bonding method was Ar ion activation, and the bonding strength was 2.5 J / m. 2 The first stripping temperature was 300℃ and the time was 30 min; the surface roughness Ra of the first bond obtained after the first polishing was 0.12 nm.

[0189] The 3C-SiC layer used in the second ion implantation is a 4° off-center 3C-SiC single crystal layer in the <11-20> direction; the implantation dose of the second ion implantation is 12 × 10⁻⁶. 15 atom / cm 2 The injection energy was 85 keV, the injection angle was 20°, and the injection depth was 1 μm; the second bonding method was Ar ion activation, and the bonding strength was 1.65 J / m. 2 The second stripping temperature was 150℃ and the time was 45 min; the surface roughness Ra of the second bond obtained after the second polishing was 0.02 nm.

[0190] The 4H-SiC layer used in the third ion implantation is a 4° 4H-SiC single crystal layer with a <11-20> orientation; the implantation dose of the third ion implantation is 20 × 10⁻⁶. 15 atom / cm 2 The injection energy was 80 keV, the injection angle was 5°, and the injection depth was 1 μm; the third bonding method was Ar ion activation, and the bonding strength was 1.88 J / m. 2 The third stripping temperature is 150℃ and the time is 45 min; the surface roughness Ra of the composite substrate obtained after the third polishing is 0.04 nm.

[0191] This embodiment provides an epitaxial structure, which comprises, from bottom to top, the following:

[0192] The composite substrate 100, buffer layer 200, first N-type 4H-SiC layer 300, second N-type 4H-SiC layer 400, first P-type 3C-SiC layer 500, and second P-type 3C-SiC layer 600.

[0193] The preparation process is as follows:

[0194] The composite substrate was sequentially etched, a buffer layer was grown, a first 4H-SiC layer was grown, a second 4H-SiC layer was grown, a first P-type 3C-SiC layer was grown, and a second P-type 3C-SiC layer was grown to obtain an epitaxial structure.

[0195] The etching process uses a carrier gas flow rate of 100 slm, a carbon source gas flow rate of 20 sccm, a temperature of 1520℃, a pressure of 100 mbar, and a time of 2 min.

[0196] The flow rate of the carrier gas used in the growth of the buffer layer is 100 slm, the flow rate of the silicon source gas used is 100 sccm, the flow rate of the carbon source gas used is 30 sccm, the flow rate of the N-type dopant used is 20 sccm, the growth temperature is 1520 °C, the growth pressure is 100 mbar, the thickness of the buffer layer obtained is 0.5 μm, and the doping concentration of the buffer layer obtained is 1 x 1018 atom / cm 17 3 ;

[0197] The flow rate of the carrier gas used in the growth of the first N-type 4H-SiC layer is 100 slm, the flow rate of the silicon source gas used is 600 sccm, the flow rate of the carbon source gas used is 400 sccm, the flow rate of the N-type dopant used is 10 sccm, the growth temperature is 1520 °C, the growth pressure is 100 mbar, the thickness of the N-type 4H-SiC layer obtained is 30 μm, and the doping concentration of the N-type 4H-SiC layer obtained is 2 x 1019 atom / cm 16 3 ;

[0198] The flow rate of the carrier gas used in the growth of the second N-type 4H-SiC layer is 100 slm, the flow rate of the silicon source gas used is 600 sccm, the flow rate of the carbon source gas used is 400 sccm, the flow rate of the N-type dopant used is 10 sccm, the growth temperature is 1520 °C, the growth pressure is 100 mbar, the thickness of the N-type 4H-SiC layer obtained is 0.5 μm, and the doping concentration of the N-type 4H-SiC layer obtained is 2 x 1019 atom / cm 16 3 ;

[0199] The flow rate of the carrier gas used in the growth of the first P-type 3C-SiC layer is 100 slm, the flow rate of the silicon source gas used is 400 sccm, the flow rate of the carbon source gas used is 800 sccm, the flow rate of the P-type dopant used is 5 sccm, the growth temperature is 1350 °C, the growth pressure is 100 mbar, the growth rate is 1 μm / h, the thickness of the P-type 3C-SiC layer obtained is 1 μm, and the doping concentration of the P-type 3C-SiC layer obtained is 2 x 1019 atom / cm 16 3 ;

[0200] ​​​​In the growth of the second P-type 3C-SiC layer, the flow rate of the carrier gas was 100 slm, the flow rate of the silicon source gas was 800 scmm, the flow rate of the carbon source gas was 400 sccm, the flow rate of the P-type dopant was 80 sccm, the growth temperature was 1350℃, the growth pressure was 100 mbar, the growth rate was 2 μm / h, the thickness of the obtained P-type 3C-SiC layer was 0.5 μm, and the doping concentration of the obtained P-type 3C-SiC layer was 1×10⁻⁶. 17 atom / cm 3 ;

[0201] In this embodiment, the carrier gas used is hydrogen, the silicon source gas used is SiHCl3, the carbon source gas used is C2H4, the N-type dopant used is NH3, and the P-type dopant used is TMAl.

[0202] Example 4

[0203] This embodiment provides a composite substrate, which includes: a polycrystalline SiC layer 1, a first 4H-SiC layer 2, a 3C-SiC layer 3, and a second 4H-SiC layer 4 bonded sequentially;

[0204] The thickness of the polycrystalline SiC layer 1 is 370 μm; the thickness of the first 4H-SiC layer 2 is 0.7 μm; the thickness of the 3C-SiC layer 3 is 0.3 μm; and the thickness of the second 4H-SiC layer 4 is 0.7 μm.

[0205] The preparation process is as follows:

[0206] The 4H-SiC layer implanted with the first ion is bonded to the polycrystalline SiC layer, and then subjected to the first peeling and the first polishing to obtain the first bonded body;

[0207] The first bonded body and the 3C-SiC layer implanted by the second ion are bonded together, followed by a second peeling and a second polishing to obtain the second bonded body;

[0208] The second bond and the 4H-SiC layer implanted by the third ion are bonded together in the third way, and then the composite substrate is obtained by third peeling and polishing.

[0209] The 4H-SiC layer used in the first ion implantation includes an N doping concentration of 1×10⁻⁶. 19 atom / cm 3 A 4° 4H-SiC single crystal layer with a <11-20> orientation; the implantation dose of the first ion implantation is 12 × 10⁻⁶. 15 atom / cm 2 The injection energy was 90 keV, the injection angle was 20°, and the injection depth was 1 μm; the first bonding method was Ar ion activation, and the bonding strength was 1.8 J / m.2 ; the first peeling temperature is 150℃, and the time is 45min; the surface roughness Ra of the first bonding body obtained after the first polishing is 0.11nm;

[0210] The 3C-SiC layer used in the second ion implantation is a <11-20> direction 4° 3C-SiC single crystal layer; the implantation dose of the second ion implantation is 20×10 15 atom / cm 2 , the implantation energy is 95keV, the implantation angle is 5°, and the implantation depth is 0.5μm; the bonding mode of the second bonding is Ar ion activation, and the bonding strength is 1.85J / m 2 ; the second peeling temperature is 300℃, and the time is 30min; the surface roughness Ra of the second bonding body obtained after the second polishing is 0.08nm;

[0211] The 4H-SiC layer used in the third ion implantation is a <11-20> direction 4° 4H-SiC single crystal layer; the implantation dose of the third ion implantation is 25×10 15 atom / cm 2 , the implantation energy is 80keV, the implantation angle is 20°, and the implantation depth is 0.5μm; the bonding mode of the third bonding is Ar ion activation, and the bonding strength is 1.95J / m 2 ; the third peeling temperature is 300℃, and the time is 30min; the surface roughness Ra of the composite substrate obtained after the third polishing is 0.12nm.

[0212] The present embodiment provides an epitaxial structure, which comprises, from bottom to top, in sequence:

[0213] The composite substrate 100, the buffer layer 200, the first N-type 4H-SiC layer 300, the second N-type 4H-SiC layer 400, the first P-type 3C-SiC layer 500, and the second P-type 3C-SiC layer 600.

[0214] The preparation process is as follows:

[0215] The composite substrate is sequentially subjected to etching, buffer layer growth, first 4H-SiC layer growth, second 4H-SiC layer growth, first P-type 3C-SiC layer growth, and second P-type 3C-SiC layer growth to obtain an epitaxial structure;

[0216] The flow rate of the carrier gas used in the etching is 500slm, the flow rate of the carbon source gas is 10sccm, the temperature is 1580℃, the pressure is 50mbar, and the time is 1min;

[0217] The flow rate of the carrier gas used in the growth of the buffer layer was 500 slm, the flow rate of the silicon source gas was 50 scmm, the flow rate of the carbon source gas was 80 sccm, the flow rate of the N-type dopant was 30 sccm, the growth temperature was 1580℃, the growth pressure was 50 mbar, the thickness of the resulting buffer layer was 2 μm, and the doping concentration of the resulting buffer layer was 2 × 10⁻⁶. 18 atom / cm 3 ;

[0218] The flow rate of the carrier gas used in the growth of the first N-type 4H-SiC layer was 500 slm, the flow rate of the silicon source gas was 300 scmm, the flow rate of the carbon source gas was 600 sccm, the flow rate of the N-type dopant was 5 sccm, the growth temperature was 1580℃, the growth pressure was 50 mbar, the thickness of the resulting N-type 4H-SiC layer was 5 μm, and the doping concentration of the resulting N-type 4H-SiC layer was 0.5 × 10⁻⁶. 16 atom / cm 3 ;

[0219] In the growth of the second N-type 4H-SiC layer, the flow rate of the carrier gas was 500 slm, the flow rate of the silicon source gas was 300 scmm, the flow rate of the carbon source gas was 600 sccm, the flow rate of the N-type dopant was 5 sccm, the growth temperature was 1580℃, the growth pressure was 50 mbar, the thickness of the obtained N-type 4H-SiC layer was 2 μm, and the doping concentration of the obtained N-type 4H-SiC layer was 4 × 10⁻⁶. 16 atom / cm 3 ;

[0220] The flow rate of the carrier gas used in the growth of the first P-type 3C-SiC layer was 500 slm, the flow rate of the silicon source gas was 800 scmm, the flow rate of the carbon source gas was 400 sccm, the flow rate of the P-type dopant was 10 sccm, the growth temperature was 1400℃, the growth pressure was 50 mbar, the growth rate was 2 μm / h, the thickness of the obtained P-type 3C-SiC layer was 0.5 μm, and the doping concentration of the obtained P-type 3C-SiC layer was 1×10⁻⁶. 16 atom / cm 3 ;

[0221] The flow rate of the carrier gas used in the growth of the second P-type 3C-SiC layer was 500 slm, the flow rate of the silicon source gas was 400 scmm, the flow rate of the carbon source gas was 800 sccm, the flow rate of the P-type dopant was 50 sccm, the growth temperature was 1400℃, the growth pressure was 50 mbar, the growth rate was 1 μm / h, the thickness of the obtained P-type 3C-SiC layer was 2 μm, and the doping concentration of the obtained P-type 3C-SiC layer was 5 × 10⁻⁶. 17 atom / cm3 ;

[0222] In this embodiment, the carrier gas used is hydrogen, the silicon source gas used is SiH2C12, the carbon source gas used is C3H8, the N-type dopant used is N2, and the P-type dopant used is TMAl.

[0223] Comparative Example 1

[0224] The difference from Example 1 is that the first N-type 4H-SiC layer is not provided in the epitaxial structure.

[0225] Comparative Example 2

[0226] The difference from Example 1 is that the second N-type 4H-SiC layer is not provided in the epitaxial structure.

[0227] Comparative Example 3

[0228] The difference from Example 1 is that the first P-type 3C-SiC layer is not provided in the epitaxial structure.

[0229] Comparative Example 4

[0230] The difference from Example 1 is that the second P-type 3C-SiC layer is not provided in the epitaxial structure.

[0231] The epitaxial structures obtained in the examples and comparative examples are tested for breakdown voltage according to GB / T 29332-2012 to characterize the voltage withstanding performance, and the results are shown in Table 1.

[0232] Table 1

[0233] Breakdown voltage / V Example 1 1657 Example 2 1734 Example 3 1638 Example 4 1724 Comparative Example 1 1589 Comparative Example 2 1592 Comparative Example 3 1585 Comparative Example 4 1579

[0234] As can be seen from Table 1, the scheme provided by the present application can form a quantum well at the connecting interface between the 3C-SiC layer and the 4H-SiC layer by adopting a specifically designed structure, so that the stacking faults are extended to the interface, thereby avoiding the stacking faults from extending to the single crystal layer, and even the epitaxial layer, so as to improve the voltage withstanding performance, and the obtained composite substrate has a low surface free energy, which can prevent the thin single crystal layer from being etched through.

[0235] The preferred embodiments of the present application are described in detail above, but the present application is not limited to the specific details in the above-described embodiments, and various simple modifications can be made to the technical solutions of the present application within the technical concept of the present application, and these simple modifications all belong to the protection scope of the present application.

[0236] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction, and in order to avoid unnecessary repetition, the present application will not further describe various possible combination manners.

[0237] Furthermore, various different embodiments of the present application can be combined with each other as long as they do not violate the spirit of the present application, and should be considered as disclosed in the present application.

Claims

1. A composite substrate, characterized by, The composite substrate comprises: a polycrystalline SiC layer, a first 4H-SiC layer, a 3C-SiC layer and a second 4H-SiC layer arranged in sequence; The thickness of the polycrystalline SiC layer is greater than the thickness of the first 4H-SiC layer, the 3C-SiC layer and the second 4H-SiC layer respectively; The thickness of the polycrystalline SiC layer is 330-370 μm; The thickness of the first 4H-SiC layer is 0.3-0.7 μm; The thickness of the 3C-SiC layer is 0.3-0.7 μm; The thickness of the second 4H-SiC layer is 0.3-0.7 μm.

2. An epitaxial structure, characterized by, The epitaxial structure comprises the composite substrate according to claim 1.

3. The epitaxial structure of claim 2, wherein, The epitaxial structure comprises, from bottom to top, in sequence: a composite substrate, a buffer layer, a first N-type 4H-SiC layer, a second N-type 4H-SiC layer, a first P-type 3C-SiC layer and a second P-type 3C-SiC layer; The thickness of the first N-type 4H-SiC layer is greater than the thickness of the second N-type 4H-SiC layer.

4. The epitaxial structure of claim 3, wherein, The thickness of the buffer layer is 0.5-2 μm; The thickness of the N-type 4H-SiC layer grown from the first N-type 4H-SiC layer is 5-30 μm; The thickness of the N-type 4H-SiC layer grown from the second N-type 4H-SiC layer is 0.5-2 μm.

5. The epitaxial structure of claim 3, wherein, The thickness of the P-type 3C-SiC layer grown from the first P-type 3C-SiC layer is 0.5-1 μm; The thickness of the P-type 3C-SiC layer grown from the second P-type 3C-SiC layer is 0.5-2 μm.

6. A device, characterized by The device comprises the composite substrate according to claim 1.

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